General Reactions of a Centipede 



SUSIE CASE 



This paper deals with the locomotion and general reactions resulting from 

 experimentation upon the nervous system of centipedes. The nervous systems of these 

 forms are very good for such experimentation, as the ganglia are distinct and widely 

 separated. 



There seem to be but three or four papers on the subject — two of these being on 

 the physiology of the brain and not behavior, and one, "On the Movements of Milli- 

 pedes and Centipedes" by E. Ray Lankester. I should like to mention several points 

 which were observed along this last line. The locomotion of the centipede can be 

 better emphasized by comparing it with that of the millipede. In the millipede one 

 of the most apparent characteristics is the movement of the legs in waves, the pairs 

 on opposite sides moving together, identically. The legs form groups of two pairs 

 to a segment and these start the motion from the tail end forward. From five to 

 eight distinct waves can be counted when all the legs are in motion. Millipedes 

 move straight forward. On the other hand, the centipede as stated by Lankester, 

 "contributes the serpentine stroke to the process of locomotion." It does not have 

 the distinct waves mentioned in locomotion of the millepede. The legs on the opposite 

 side do not move identically but are antogonistic in phase; and move in perfect 

 harmony unless there be some injury to the nervous system, which controls locomotion. 

 I agree with Lankester that it is most probable that the condition presented by the 

 centipede in locomotion is a higher development than that shown by the millipede. 

 The wave movement suggests a type found in lower invertebrates. 



Th reverse locomotion of the centipede is very interesting. Most of them persist 

 in going forward and yet in testing to find some definite result, I have discovered 

 that occasionally they will, with persuasion, go backward. Most often, however, they 

 turn the entire body instead of reversing the movements of the legs. On the other 

 hand, all millipedes with persuasion will reverse for a short distance. \\Tien one 

 goes backwards, it reverses the motion of the waves also, causing them to go from 

 head to tail instead of from tail to head. 



I have mentioned the two main observations of general behavior as to locomo- 

 tion and shall now go on to the definite experiments which were made on the 

 centipede to test specific reactions. 



First as to the method: The specimen to be operated upon was pinned out on 

 cork — the pins not being put through the centipede but across in a sufficient number of 

 places to hold it firmly. The cut was made from the dorsal side into the nervous 

 system. We tried not to make the external cut any larger than was absolutely 

 necessary. When in doubt as to the position of the injury, we examined the animal 

 after death. 



The experiments and results are as follows: 

 Experiment /...Twelfth connective cut on right side. Results: 

 1. Some lack of movement in legs near cut and on same side, probably due to 

 injury of muscles. 



